Illuminating device, electro-optical device, and electronic apparatus

ABSTRACT

An illuminating device includes a plurality of light sources, a light guide plate that has plate surfaces on front and rear sides and a plurality of end faces formed around the plate surfaces, receives light emitted from the plurality of light sources through a light incident surface, which is at least one end face among the plurality of end faces, and emits the light through a light-emitting surface, which is one of the plate surfaces, a plurality of photodetectors that are disposed to face the end faces or the plate surfaces of the light guide plate, and a light source control unit that controls light emission of the plurality of light sources on the basis of the output of the plurality of photodetectors. The plurality of photodetectors include at least two photodetectors including light receiving surfaces that face the end faces or the plate surfaces in different directions from each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. Ser. No.11/697,494 filed Apr. 6, 2007, claiming priority to Japanese PatentApplication No. 2006-110916, filed Apr. 13, 2006, all of which areincorporated by reference in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to an illuminating device, to anelectro-optical device, and to an electronic apparatus. In particular,the invention relates to a structure of an illuminating device having afunction of controlling light emission of light sources according todetection values of photodetectors.

2. Related Art

In a known illuminating device, light emitted from light sources, suchas LEDs, is made incident on a light guide plate, propagates through thelight guide plate, and is emitted from a light-emitting surface of thelight guide plate. Such an illuminating device has been used as, forexample, a planar illuminating device, such as a backlight, forilluminating a liquid crystal panel.

In the illuminating device, uniformity of luminance of light emittedfrom a light-emitting surface needs to be ensured, and white balance ofthe emitted light needs to be ensured. Since light sources havevariations in luminance and chromaticity, when a plurality of lightsources are disposed, a variation in illumination light may be furtherincreased when the individual light sources having different levels ofluminance and chromaticity are combined. Therefore, a method ofdetecting luminance or color tones using photodetectors, which arearranged around the light guide plate or at a light emitting side, andperforming feedback control on the luminance and the color tones of thelight source according to the detected values has been proposed (forexample, see JP-A-2005-91526, JP-A-2004-199968, and JP-A-2005-70132).

However, in the control method using the detection values of thephotodetectors, light, which is emitted from the light guide plate, isdetected using the photodetectors, and the light sources are controlledon the basis of the detection. For example, devices disclosed inJP-A-2005-91526 and JP-A-2004-199968 detects only light, which isemitted from the light guide plate in a predetermined direction.Therefore, there is a case in which detection values of thephotodetectors may not sufficiently reflect the entirety of theillumination light emitted from the light-emitting surface of the lightguide plate. Even when the light sources are controlled on the basis ofthe detection values, the illumination light is not sufficientlycontrolled.

Further, in a device disclosed in JP-A-2005-70132, in order to detectlight incident on a display cell, a photodetector is correspondinglyarranged on one substrate surface of the display cell. Therefore, it maynot be possible to form only the illuminating device, and a structure ofthe display cell or a wiring line installation becomes complex, therebyincreasing manufacturing costs.

SUMMARY

An advantage of some aspects of the invention is that it provides anilluminating device which is capable of controlling illumination lightwith high accuracy by accurately detecting the illumination light of theilluminating device without complicating a structure of one illuminatingdevice or a wiring line installation, and an electro-optical deviceincluding the illuminating device.

According to a first aspect of the invention, an illuminating deviceincludes a plurality of light sources, a light guide plate that hasplate surfaces on front and rear sides and a plurality of end facesformed around the plate surfaces, receives light emitted from theplurality of light sources through a light incident surface, which is atleast one end face among the plurality of end faces, and emits the lightthrough a light-emitting surface, which is one of the plate surfaces, aplurality of photodetectors that are disposed to face the end faces orthe plate surfaces of the light guide plate, and a light source controlunit that controls light emission of the plurality of light sources onthe basis of the output of the plurality of photodetectors. Theplurality of photodetectors include at least two photodetectorsincluding light receiving surfaces that face the end faces or the platesurfaces in different directions from each other.

According to this structure, since the plurality of photodetectorsinclude at least two photodetectors that include light receivingsurfaces that are disposed to face the end faces or the plate surfacesfacing in different directions from each other, it is possible toaccurately detect light that is emitted along different directions fromthe light guide plate. Therefore, by using the detection values, it ispossible to perform the control by sufficiently reflecting a state ofillumination light emitted from the light emitting surface of the lightguide plate.

Preferably, the plurality of photodetectors include at least twophotodetectors that have the light receiving surfaces thereof disposedat positions distant from the light receiving surface by differentdistances. Since the light receiving surfaces are arranged at positionsdistant from the light receiving surface by different distances, it ispossible to detect light that is emitted at different positions asviewed in a propagation direction of the light of the light guide plate.Therefore, it is possible to reduce an effect on the control due to avariation of the illumination light as viewed in the propagationdirection, and thus it is possible to perform the control while moreaccurately reflecting the illumination light.

Preferably, the plurality of photodetectors include at least twophotodetectors that have light receiving surfaces thereof that face acentral portion and one end portion in an arrangement direction of theplurality of light sources are arranged, or both end portions of thearrangement direction, when viewed from the light incident surface.Therefore, as the light receiving surfaces that are separated from eachother along the direction where the plurality of light sources arearranged are formed, it is possible to reduce an effect on the controldue to a variation of the arranged direction of the light sources.Accordingly, it is possible to perform the control by more accuratelyreflecting the illumination light.

Preferably, the light guide plate has a rectangular shape in plan view,and the plurality of photodetectors include at least two adjacentphotodetectors that have light receiving surfaces that are disposed toface two of the end faces and the plate surfaces of the light guideplate that are adjacent to each other. Therefore, in the light guideplate having the rectangular shape viewed in plane, the light receivingsurfaces disposed to face the two adjacent end faces or the platesurfaces, respectively. Since it is possible to detect light that isemitted toward a direction at 90 degrees from the light guide plate, itis possible to perform the control while more accurately reflecting theillumination light.

Preferably, the light source control unit collectively controls theplurality of light sources on the basis of representative values, whichare derived from detection values detected by the plurality ofphotodetectors. Since the plurality of light sources are collectivelycontrolled on the basis of representative values, which are derived fromdetection values detected by the plurality of photodetectors, it ispossible to achieve simplification of the light source control unit.Therefore, it is possible to achieve a control state in which theillumination light is sufficiently reflected, and reduce manufacturingcosts. Here, the representative value may include an average value of aplurality of detection values, a weighted average value, the sum, thelinear sum, or a median value. In particular, for the easy deduction,the average value or the sum may be preferably used. Further, since theweight can be arbitrarily set for various situations, the average valueand the sum may be preferably used.

Preferably, the light sources control chromaticity of emitted light, thephotodetectors output detection values with which chromaticity ofdetected light can be derived, and the light source control unitcontrols collectively chromaticity of emitted light of the plurality oflight sources on the basis of representative values of chromaticity thatare derived from the detection values of the plurality ofphotodetectors. Therefore, it is possible to easily control thechromaticity of the illumination light, for example, white balance.

Preferably, the light sources control luminance of emitted light, thephotodetectors output detection values with which luminance of detectedlight can be derived, and the light source control unit collectivelycontrols luminance of emitted light of the plurality of light sources onthe basis of representative values of luminance that are derived fromthe detection values of the plurality of photodetectors. Therefore, itis possible to easily control the luminance of the illumination light.

According to a second aspect of the invention, an electro-optical deviceincludes the above-described illuminating device, and anelectro-electronic panel that are disposed on a light emitting side ofthe illuminating device and functions on the basis of illumination lightof the illuminating device. Since it is possible to reduce variations inluminance or chromaticity by the illuminating device, it is possible toobtain reproducibility of good display of color tones.

According to a third aspect of the invention, an electronic apparatusincludes the electro-optical device. Examples of the electronicapparatus may include various electronic apparatus using electro-opticaldevices on display units, for example, computer devices, displaydevices, cellular phones, electronic watches, and projectors.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers refer to like elements.

FIG. 1 is a schematic plan view illustrating the planar arrangement ofan illuminating device according to a first embodiment of the invention.

FIG. 2 is a schematic longitudinal cross-sectional view taken along theline II-II of FIG. 1 of an electro-optical device to which theilluminating device according to the first embodiment is applied as abacklight.

FIG. 3 is an enlarged partial cross-sectional view schematically showingthe positional relationship between a light guide plate andphotodetectors.

FIG. 4 is a chromaticity diagram illustrating a control method.

FIG. 5 is a graph showing average intensities of RGB components ofdetected light and previously set values corresponding to the averageintensities.

FIG. 6 is a schematic plan view illustrating the planar arrangement ofan illuminating device according to a second embodiment.

FIG. 7 is a schematic plan view illustrating the planar arrangement ofan illuminating device according to a third embodiment.

FIG. 8 is a schematic plan view illustrating the planar arrangement ofan illuminating device according to a fourth embodiment.

FIG. 9 is a schematic plan view illustrating the planar arrangement ofan illuminating device according to a fifth embodiment.

FIG. 10A is a schematic plan view illustrating the planar arrangement ofan illuminating device according to a sixth embodiment.

FIG. 10B is a schematic longitudinal cross-sectional view taken alongthe line XB1-XB1 of FIG. 10A.

FIG. 11A is a schematic plan view illustrating the planar arrangement ofan illuminating device according to a seventh embodiment.

FIG. 11B is a schematic longitudinal cross-sectional view taken alongthe line XIB1-XIB1 of FIG. 11A.

FIG. 12 is a schematic perspective view illustrating the appearance of anotebook computer according to an embodiment of an electronic apparatus.

FIG. 13 is a schematic perspective view illustrating the appearance of acellular phone according to another embodiment of the electronicapparatus.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an illuminating device, an electro-optical device, and anelectronic apparatus according to embodiments of the invention will bedescribed with reference to the accompanying drawings.

First Embodiment Illuminating Device

FIG. 1 is a schematic view illustrating the structure of an illuminatingdevice according to a first embodiment of the invention. An illuminatingdevice 100 includes a plurality of light sources (in the example of FIG.1, six light sources) 111, 112, 113, 114, 115, and 116, a light guideplate 120 that receives light emitted from the light sources from alight incident surface 120 a, which is one of the end faces thereof, andemits the light from a light-emitting surface 121 that is one of theplate surfaces thereof, a plurality of photodetectors (in the example ofFIG. 1, three photodetectors) 131, 132, and 133 that are disposed atdifferent positions around the light guide plate 120, a detectingcircuit 140 that calculates a representative value on the basis ofdetection values that are obtained individually by the photodetectors131, 132, and 133, and a control circuit 150 that controls the lightsources 111 to 116 on the basis of a result obtained by comparing therepresentative value with a predetermined set value. Here, the detectingcircuit 140 and the control circuit 150 form the above-described lightsource control unit.

The light guide plate 120 may be, for example, a plate-like body thathas a rectangular shape in plan view and is formed of acryl orpolycarbonate having a bending rate of approximately 1.5, and includes aplurality of end faces 120 a, 120 b, 120 c, and 120 d (in the example ofFIG. 1, four end faces) and two plate surfaces 121 and 122 at front andrear sides. The light guide plate 120 allows incident light introducedfrom the light incident surface 120 a, which is one of the end faces, topropagate through the light guide plate, and emits the light through thelight-emitting surface 121 (top surface), which is one of the platesurfaces. Further, a light deflection unit (not shown), such as a fineuneven structure or a dot printed layer, is formed on the bottom surface122, which is the other plate surface of the light guide plate 120. Inaddition, a light reflective sheet 130 is disposed below the bottomsurface 122 of the light guide plate 120. The light reflective sheetreflects the light, which propagates through the light guide plate 120and emitted from the bottom surface 122, makes the light incident on theinside of the light guide plate 120 again, and finally the light isemitted from the light-emitting surface 121.

Here, the plurality of light sources 111 to 116 are arranged in astraight line along the light incident surface 120 a of the light guideplate 120 with predetermined gaps therebetween. Each of the lightsources includes one set of three light emitting units that emit lightof different wavelengths of three colors, i.e., red (R), green (G), andblue (B). Each of the R light emitting unit, the G light emitting unit,and the B light emitting unit adjusts luminance in accordance with theamount of current supplied, and are generally set so that the entirelight source emits white light. The light emitting units may include,for example, LEDs (light emitting diodes).

Further, the plurality of photodetectors 131, 132, and 133 include lightreceiving surfaces, which are provided with a plurality of lightreceiving units that can detect light intensities in differentwavelength ranges. Specifically, each of the photodetectors includes a Rlight receiving unit having a R filter, a G light receiving unit havinga G filter, and a B light receiving unit having a B filter, such thateach of the photodetectors detects light intensity of a R lightcomponent, a G light component, and a B light component according tocharacteristics of the respective filters. Each of the light receivingunits may include, for example, phototransistors or photodiodes.

Further, the plurality of photodetectors 131, 132, and 133 are disposedfacing the end faces 120 b, 120 c, and 120 d, respectively, with thelight incident surface 120 a of the light guide plate 120 being the onlyend face of one light guide plate 120 not faced by a photodetector. Theplurality of photodetectors 131, 132, and 133 detect light that isemitted through each of the end faces of the light guide plate 120. Theplurality of photodetectors 131, 132, and 133 are disposed such that theorientations of the light receiving surfaces with respect to the lightguide plate 120 are different from one another. Specifically, the lightreceiving surfaces face the end faces 120 b, 120 c, and 120 d of thelight guide plate 120, which face in different directions. Thephotodetectors each receive light from different directions.

More specifically, as shown in FIG. 1, the photodetector 131 is disposedto face a portion of the end face 120 b that is one (left side) end facecrossing (orthogonal to) the light incident surface 120 a of the lightguide plate 120, the portion being disposed far from the light incidentsurface 120 a, that is, an end portion that is adjacent to the end face120 c facing the light incident surface 120 a. Further, thephotodetector 132 is disposed to substantially face a central portion ofthe end face 120 c that faces the light incident surface 120 a of thelight guide plate 120. Further, the photodetector 133 is disposed toface a portion of the end face 120 d that is the other (right side) endface crossing (orthogonal to) the light incident surface 120 a, theportion that is disposed close to the light incident surface 120 a, thatis, an end portion being disposed close to the light incident surface120 a.

Accordingly, the photodetector 131 measures light that is emitted towardone side direction from the end portion of the end face 120 b, which isdisposed far from the light incident surface 120 a. Further, thephotodetector 132 measures light emitted from the substantially centralportion of the end face 120 c in almost the same direction as apropagation direction of light. Furthermore, the photodetector 133measures light that is emitted from the end portion of the end face 120d, which is disposed close to the light incident surface 120 a, in theother side direction.

Further, the photodetectors 131, 132, and 133 may be positioned, forexample, as shown in FIG. 3A, so that the light receiving surfaces 131a, 132 a, and 133 a face the end faces 120 b, 120 c, and 120 d of thelight guide plate 120, respectively. Alternatively, the photodetectorsmay be positioned as follows. As shown in FIG. 3B, the light receivingsurfaces 131 a, 132 a, and 133 a do not directly face the end faces 120b, 120 c, and 120 d, but light emitted from the end faces 120 b, 120 c,and 120 d is made incident on the light receiving surface through alight guiding member (reflector in the drawing) 160.

In the example shown in the drawing, the photodetectors 131, 132, and133 are disposed to face the end faces 120 b, 120 c, and 120 d of thelight guiding plate 120, respectively. Alternatively, the photodetectors131, 132, and 133 may be disposed to face portions of the light-emittingsurface 121 or the bottom surface 122. In theses cases, in order not tointerfere with an illumination range of the illuminating device 100, thephotodetectors 131, 132, and 133 may be disposed to face an outercircumferential portion (a portion separated from a driving area of anelectro-optical panel to be described below) of the light-emittingsurface 121 or the bottom surface 122.

For example, as shown in FIG. 3C, the photodetectors 131, 132, and 133may be disposed to face the bottom surface 122 of the light guide plate120. At this time, the photodetectors face upward such that the lightreceiving surfaces 131 a, 132 a, and 133 a thereof face the bottomsurface 122. Further, it is preferable that the photodetectors 131, 132,and 133 be disposed between the light guide plate 120, and a frame body911 that accommodates the light guide plate 120. In contrast, thephotodetectors may be disposed above the light-emitting surface 121 withthe light receiving surfaces thereof facing downward.

Further, as shown in FIG. 3D, a notch 120 g is formed in a bottomportion of the end face of the light guide plate 120, and each of thephotodetectors 131, 132, and 133 is accommodated in the notch 120 g.Therefore, as compared with the case in FIG. 3C, the thickness of theilluminating device can be reduced. At this time, each of the lightreceiving surfaces 131 a, 132 a, and 133 a of the photodetectors facesan internal surface 120 ga of the notch 120 g. Further, since each ofthe light receiving surfaces is disposed to face the internal surface120 ga, it is possible to form the illuminating device having a smallersize as compared with the case in FIG. 3A.

The detecting circuit 140 shown in FIG. 1 calculates a representativevalue of the respective detection values that are output by theplurality of photodetectors 131, 132, and 133, and outputs thecalculated representative value to the control circuit 150. In general,the representative value may be, for example, an average value. However,the representative value may a median value, a weighted average valueset in accordance with an appropriate weight coefficient, a simple sum,or a linear sum set in accordance with an appropriate coefficient.Further, the detecting circuit 140 outputs a representative value ofchromaticity on the basis of the detection values detected by each ofthe photodetectors. Alternatively, as described below, the detectingcircuit 140 may obtain a representative value of luminance on the basisof each of the detection values detected by the photodetectors, orobtain representative values of both the chromaticity and the luminance.Hereinafter, the description will be made on the assumption that anaverage value of the chromaticity is calculated by the detecting circuit140 and the control circuit 150 controls chromaticity of each of thelight sources.

In this case, for the calculation of the average value of the detectionvalues, chromaticity C1 is calculated of the basis of intensities L1 r,L1 g, and L1 b of RGB components of light that is detected by thephotodetector 131. The chromaticity C1 can be a value calculated byusing an appropriate color system. For example, since in a CIE colorsystem that is used in a chromaticity diagram shown in FIG. 4,chromaticity is expressed according to x and y, the chromaticity iscalculated, for example, in the form of C1 (x1 and y1). In the samemanner, chromaticity C2 (x2 and y2) is calculated on the basis ofdetection values of the photodetector 132, and chromaticity C3 (x3 andy3) is calculated on the basis of detection values of the photodetectors133. Then, an average value P (xp and yp) of three chromaticities C1,C2, and C3 is obtained. Here, the equations used are as follows:xp=(x1+x2+x3)/3 and yp=(y1+y2+y3)/3.

The control circuit 150 compares the average value P (xp and yp), whichis output by the detecting circuit 140 as described above, with apreviously set value A (xa and ya) that expresses predeterminedchromaticity so as to calculate chromaticity difference ΔC (Δx and Δy).Here, the equations used are as follows: Δx=xp−xa and Δy=yp−ya. Inaddition, on the basis of the chromaticity difference ΔC, controlsignals SR, SG, and SB are output by the control circuit 150. Here, thecontrol signals SR, SG, and SB are commonly transmitted to the lightsources 111 to 116. That is, in the light sources 111 to 116, the Rlight emitting unit (formed of the red LED and the like) that emitslight in a red range is controlled by the control signal SR, the G lightemitting unit (formed of the green LED and the like) that emits light ina green range is controlled by the control signal SG, and the B lightemitting unit (formed of the blue LED and the like) that emits light ina blue range is controlled by the control signal SB.

The control signals SR, SG and SB define values of currents that aresupplied to the light emitting units, and the like, and adjust lightemitted from the light sources 111 to 116 so as to reduce thechromaticity difference AC.

For example, as shown in FIG. 4, when an emission color of the R lightemitting unit of each of the light sources 111 to 116 is CR, an emissioncolor of the G light emitting unit thereof is CG, and an emission colorof the B light emitting unit thereof is CB, and the light sources 111 to116 can reproduce colors in a triangle of CR-CG-CB. As light intensityof each of the emission colors CR, CG, and CB is changed on the basis ofthe difference AC between the average value P and the previously setvalue A, in order to reduce the difference AC, that is, in order toapproximate the average value P to the previously set value A, thecontrol signals SR, SG, and SB are generated.

The light source control unit may be constructed so as to control thelight sources according to a different method from the above-describedmethod. For example, for the average value of the chromaticity, whenintensities of RGB components of light, which are detected by thephotodetector 131, are L1 r, L1 g, and L1 b, intensities of RGBcomponents of light, which are detected by the photodetector 132, are L2r, L2 g, and L2 b, and intensities of RGB components of light, which aredetected by the photodetector 133, are L3 r, L3 g, and L3 b, averageintensity Pr of the R components of the three photodetectors 131, 132,and 133, average intensity Pg of the G components thereof, and averageintensity Pb of the B components thereof can be used. Here, theequations used are as follows: Pr=(L1 r+L2 r+L3 r)/3, Pg=(L1 g+L2 g+L3g)/3, and Pb=(L1 b+L2 b+L3 b)/3.

FIG. 5 shows the average values Pr, Pg, and Pb of the light intensitiesof the RGB components. Then, the average values Pr, Pg, and Pb arecompared with previously set values Ar, Ag, and Ab corresponding to thelight components, respectively, and differences ΔIr=Pr−Ar, AIg=Pg−Ag,and ΔIb=Pb−Ab of the light intensities of the respective components areobtained. Further, the control signals SR, SG, and SB corresponding tothe R light emitting unit, the G light emitting unit, and the B lightemitting unit are decreased or increased according to the differences,and output to the light sources 111 to 116, thereby setting thechromaticity of the emitted light of each of the light sources. Even inthis way, it is possible to control the light sources such that thedifference between the average value P and the previously set value A isreduced.

As described above, even when either method is used, according to thisembodiment, chromaticity (white balance) of illumination light that isemitted from the light-emitting surface 121 of the light guide plate 120can be feedback-controlled. In this case, it is preferable that theplurality of light sources 111 to 116 be collectively controlled by thecommon control signals, because the control circuit 150 can be simplyand easily formed. Even in this way, since an object of the chromaticitycontrol according to this embodiment is reproducibility of thechromaticity of the entirety of the illumination light that is emittedfrom the light-emitting surface 121 of the light guide plate 120,sufficient control effect with respect to a variation in chromaticitylevel of the entirety of the illumination light can be obtained by thecombination of the characteristics of the plurality of light sources 111to 116.

Further, the above-described light source control unit may only performthe above-described control when a starting switch (not shown) isoperated or a predetermined starting signal is input. Further, ingeneral, the control may be performed with a predetermined period ortiming.

Further, in the above description, the chromaticity is controlled.However, when luminance is controlled, the representative value ofluminance from the detection values of the plurality of photodetectorsin the detecting circuit 140, for example, the average value iscalculated, and according to a result obtained by comparing therepresentative value of the luminance with the previously set value ofluminance, it is possible to control the plurality of light sources. Inthis case, the luminance is preferably adjusted such that the luminanceitself is not changed. However, as described above, the chromaticity maybe controlled and at the same time, the luminance may also becontrolled. In this way, both the chromaticity and the luminance of theillumination light can be made to approximate the previously set values.

In particular, the representative value of the luminance is not affectedby a variation in a left end portion and a right end portion, or acentral portion and both end portions of one of the plurality of endfaces of the light guide plate 120 as viewed in a direction in which thelight sources are arranged, or a variation in a portion adjacent to thelight incident surface 120 a of the light guide plate 120 and a portiondistant from the light incident surface 120 a of the light guide plate120 as viewed in a propagation direction of light in the light guideplate 120. Therefore, an average is effectively obtained by applying apredetermined weight to the detection value of each of thephotodetectors or linear sum is effectively obtained by applying aweight to the detection value with a predetermined coefficient.

According to the first embodiment of the invention, since the pluralityof photodetectors 131, 132, and 133 are disposed to face the three endfaces 120 b, 120 c, and 120 d of the light guide plate 120 that facedifferent in directions from each other, light emitted from the lightguide plate 120 in different directions can be detected through theplurality of photodetectors 131, 132, and 133. Therefore, light can bedetected while more accurately reflecting the entirety of theillumination light emitted from the light-emitting surface 121 of thelight guide plate 120. Accordingly, it is possible to perform thechromaticity control with high accuracy.

In particular, the plurality of photodetectors are disposed to face thedifferent end faces of the light guide plate 120. Also, the plurality ofphotodetectors are disposed to face portions disposed far from the lightincident surfaces of the end faces 120 b, 120 c, and 120 d, the centerportions thereof, and the portions disposed close thereto. It ispossible to perform control in a state where the entirety of theillumination light is accurately reflected.

Electro-optical Device

FIG. 2 is a schematic longitudinal cross-sectional view taken along theline II-II of FIG. 1, illustrating an electro-optical device 900 thatincludes the illuminating device 100. The electro-optical device 900uses the illuminating device 100 as a backlight. On the light-emittingsurface 121 of the illuminating device 100, a light diffusing sheet 920,and two prism sheets 930 and 940 are disposed, and an electro-opticalpanel 800 is disposed thereon.

The light diffusing sheet 920 equalizes light that is radiated on atleast a driving area of the electro-optical panel 800, and is asemi-transparent sheet that scatters or diffuses light. The lightdiffusing sheet 920 is obtained, for example, by applying resin mixedwith transparent beads to a sheet formed of transparent synthetic resin,such as polyester.

The two prism sheets 930 and 940 collect light of the illuminatingdevice 100 so as to increase front luminance of a viewing side. Forexample, each of the two prism sheets 930 and 940 is obtained bydisposing prism structures, each of which extends in a predetermineddirection and has a triangular cross-section, in a plurality of stripes.The two prism sheets 930 and 940 are disposed with light collectingdirections thereof (directions perpendicular to the extension directionof the prism structures) orthogonal to each other.

The electro-optical panel 800 is formed of a transmissive type-orsemi-transmissive type liquid crystal display body, and can use variousliquid crystal modes, such as TN (Twisted Nematic) liquid crystal andSTN (Super Twisted Nematic) liquid crystal. Further, theelectrode-optical panel 800 may include an active matrix type displaybody that uses TFTs (Thin Film Transistors), TFDs (Thin Film Diodes), orthe like, as switching elements, or a passive matrix type display body.Further, in the example in the drawings and the description below, it isassumed that the electro-optical panel 800 is formed of a transflectivetype.

In a case of the example in FIG. 2, the electro-optical panel 800 isformed by sealing liquid crystal 840 between a pair of substrates 820and 830 that are formed of glass or plastic and bonded to each otherwith a sealant 810. A polarizer 821 is attached to an external surfaceof the substrate 820 of the viewing side. Further, color filters 822having three colors of R, G, and B and a black matrix, a passivationlayer 823, pixel electrodes 824, and an alignment layer 825 aresequentially deposited over an internal surface of the substrate 820.Meanwhile, a polarizer 831 is attached to an external surface of thesubstrate 830 at the backlight side. Further, a light reflecting layer832 having openings 832 a therein, an insulating layer 833, pixelelectrodes 834, and an alignment layer 835 are sequentially depositedover an internal surface of the substrate 830.

In the electro-optical panel 800, when a voltage is applied to the pixelelectrodes 824 and 834 formed on the pair of substrates 820 and 830,respectively, an alignment state of the liquid crystal 840 iscontrolled. Since a degree of modulation with respect to a polarizedstate of illumination light a from the illuminating device 100 orexternal light b incident from the viewing side is changed,transmittance or reflectance of light in every sub-pixel SPX iscontrolled by the operation of the polarizers 821 and 831.

In the electro-optical device 900, since the illuminating device 100 isused as the backlight, transmissive display with high reproducibility isachieved by the illumination light a whose chromaticity is controlled asdescribed above.

Second Embodiment

Next, an illuminating device 200 according to a second embodiment willbe described in detail with reference to FIG. 6. FIG. 6 is a schematicplan view illustrating a planar arrangement of light sources, a lightguide plate, and photodetectors of the illuminating device 200 accordingto a second embodiment. In this embodiment, the same constituentelements as those of the illuminating device 100 according to the firstembodiment are denoted by the same reference numerals. Thus, thedescription thereof will be omitted.

This embodiment includes a plurality of photodetectors 231, 232, and 233having the same structures as the photodetectors 131, 132, and 133 ofthe illuminating device 100 according to the first embodiment. However,the photodetectors 231 and 232 are disposed to face both end portions ofleft and right of an end face 120 c of the light guide plate 120.Further, the photodetector 233 is disposed to face a bottom surface ofthe light guide plate 120. More specifically, a light receiving surfaceof the photodetector 233 is disposed to face a bottom surface portionadjacent to a central portion of the end face 120 c of the light guideplate 120.

The illuminating device 200 according to the second embodiment candetect light, which is emitted toward a light propagation direction(upper direction in FIG. 6) from both end portions of the end face 120 cof the light guide plate 120, by the two photodetectors 231 and 232,respectively. Further, the illuminating device 200 can detect light,which is emitted downward from the bottom surface of the light guideplate 120, by the photodetector 233.

In this embodiment, light receiving surfaces of the plurality ofphotodetectors 231 and 232 and the light receiving surface of thephotodetector 233 face directions different from each other, and thus,it is possible to detect light emitted toward different directions fromthe light guide plate 120. Therefore, in the same manner as the firstembodiment, it is possible to control the light sources 111 to 116 whilesufficiently reflecting the illumination light. Further, in thisembodiment, since light of both end portions along a direction in whichthe light sources 111 to 116 are arranged at the light guide plate 120can be detected by the photodetectors 231 and 232, it is possible tocontrol the illumination light by adding distribution of theillumination light along the direction in which the light sources 111 to116 are arranged. Further, since the light receiving surface of thephotodetector 233 is disposed to face the bottom surface portionadjacent to the central portion of the end face 120 c, even when thebias of the illumination light exists between the central portion andthe both end portions as viewed in the direction in which the lightsources are arranged, by taking into consideration detection values ofthe photodetectors 231 and 232, which detect the both end portions, adetection value of the photodetector 233, which detects the centralportion, it is possible to control the illumination light by removingthe effect due to the bias of the central portion and the both endportions along the direction in which the light sources are arranged.

Further, contrary to this, the photodetectors 231 and 232 may bedisposed to face the bottom surface portion adjacent to the both endportions of the end face 120 c, and the photodetector 233 may bedisposed to face the central portion of the end face 120 c. Further, thephotodetectors disposed to face the bottom surface portion may bedisposed to face the light-emitting surface 121.

Third Embodiment

Next, an illuminating device 300 according to a third embodiment will bedescribed with reference to FIG. 7. FIG. 7 is a schematic plan viewillustrating a planar arrangement of light sources, a light guide plate,and photodetectors of the illuminating device according to the thirdembodiment. Further, the same constituent elements as those of theilluminating device 100 according to the first embodiment are denoted bythe same reference numerals. Thus, the description thereof will beomitted.

In this embodiment, a photodetector 331 is disposed to face one endportion of an end face 120 c, and a photodetector 332 is disposed toface a central portion of the end face 120 c. Further, a photodetector333 is disposed to face an end face 120 d that is adjacent to an endportion opposite to the one end portion of the end face 120 c which thephotodetector 331 faces.

In this embodiment, by the photodetectors 331 and 332 that face the endportion and the central portion, respectively, of the end face 120 c, itis possible to reduce an effect on the control due to a variation of thecentral portion and the end portion along a direction in which lightsources 111 to 116 are arranged. Further, by adding the photodetector333 facing the end face 120 d, it is possible to reduce an effect on thecontrol due to a variation along a direction in which light is emitted,or a variation between both end portions along the direction in whichthe light sources are arranged. In particular, when the plurality oflight sources are arranged, due to the heat radiated from each lightsource, temperature of the light sources around the center relativelyincreases, and temperature of the light sources at the end is relativelydecreases. Therefore, a state in which the light sources emit light maybe changed, and thus, the variation of the illumination light, whenviewed in the direction of the light sources arranged, is likely toincrease. Accordingly, the above-described disposition of thephotodetectors is effective.

Meanwhile, the photodetector 333 may be disposed to face the centralportion of the end face 120 d or any one of end portions (end portion atthe light incident surface 120 a or the end face 120 c) of the end face120 d.

Fourth Embodiment

Next, an illuminating device 400 according to a fourth embodiment willbe described with reference to FIG. 8. FIG. 8 is a schematic plan viewillustrating a planar arrangement of light sources, a light guide plate,and photodetectors of an illuminating device according to a fourthembodiment. Here, the same constituent elements as those of theilluminating device 100 according to the first embodiment are denoted bythe same reference numerals. Thus, the description thereof will beomitted.

In this embodiment, a photodetector 431 is disposed to face an endportion (in the example in FIG. 8, side that is most spaced from lightsources) of an end face 120 b of a light guide plate 120, and aphotodetector 432 is disposed to face a central portion of an end face120 c of the light guide plate 120.

In this way, by only the two photodetectors 431 and 432, it is possibleto reduce an effect on the control due to a variation of light that isemitted toward a different direction from the light guide plate 120, andit is also possible to reduce an effect on the control due to avariation of light of a central portion and end portions when viewed ina direction where light sources are arranged.

Meanwhile, as indicated by dotted line in FIG. 8, the photodetector 431may be disposed to face an end portion of an end face 120 b that isdisposed close to the light sources. In this case, it is also possibleto reduce an effect on the control due to a variation in a propagationdirection of light of the light guide plate 120 by the photodetectors431 and 432. Further, in the disposition of each of the components, thephotodetector 431 may be disposed to face the end face 120 d instead ofthe end face 120 b.

Fifth Embodiment

Next, an illuminating device according to a fifth embodiment will bedescribed with reference to FIG. 9. FIG. 9 is a schematic plan viewillustrating a planar arrangement of light sources, a light guide plate,and photodetectors of an illuminating device according to a fifthembodiment. Here, the same constituent elements as those of theilluminating device 100 according to the first embodiment are denoted bythe same reference numerals. Thus, the description thereof will beomitted.

In this embodiment, a photodetector 531 is disposed to face one endportion of an end face 120 c of a light guide plate 120, and aphotodetector 532 is disposed to face a central portion of an end face120 d that is adjacent (orthogonal) to an end face 120 c that isopposite to an end portion where the photodetector 531 is disposed.

In this way, by only the two photodetectors 531 and 532, it is possibleto detect emitted light at different angles and reduce an effect on thecontrol due to a variation of left and right both sides when viewed in adirection where the light sources are arranged. It is also possible toreduce an effect on the control due to a variation between a centralportion and end portions when viewed in a propagation direction of lightof the light guide plate 120.

Meanwhile, as indicated by dotted line in FIG. 9, the photodetector 531may be disposed to face the central portion of the end face 120 c. Inthis case, it is possible to stably detect light that is emitted indirections perpendicular to each other from central portions of the endfaces 120 c and 120 d, respectively, of the light guide plate 120 by thephotodetectors 531 and 532.

Sixth Embodiment

Next, an illuminating device according to a sixth embodiment will bedescribed with reference to FIGS. 10A and 10B. FIG. 10A is a schematicplan view illustrating a planar arrangement of light sources, a lightguide plate, and photodetectors of an illuminating device according to asixth embodiment. FIG. 10B is a schematic longitudinal cross-sectionalview taken along the line XB1-XB1 of FIG. 10A. Here, the sameconstituent elements as those of the illuminating device 100 accordingto the first embodiment are denoted by the same reference numerals.Thus, the description thereof will be omitted.

In this embodiment, one photodetector 631 is disposed to face an endportion of an end face 120 c, and the other photodetector 632 isdisposed to face a central portion of a bottom surface 122 of a lightguide plate 120, that is, a bottom surface portion that is adjacent to acentral portion of an end face 120 c.

In this way, by only the two photodetectors 631 and 632, it is possibleto detect light that is emitted toward different directions from thelight guide plate 120, and it is also possible to reduce an effect onthe control due to a variation of the central portion and the endportion when viewed in a direction where the light sources are arranged.

Meanwhile, the photodetector 631 may be disposed at an end portion ofthe end face 120 c toward an end face 120 d. Further, contrary to theabove description, the photodetector 631 may be disposed to face abottom surface portion that is adjacent to the end portion of the endface 120 c, and the photodetector 632 may be disposed to face thecentral portion of the end face 120 c. Further, the photodetectordisposed to face the bottom surface portion may be disposed to face thelight-emitting surface 121, not the bottom surface 122.

Seventh Embodiment

Next, an illuminating device according to a seventh embodiment will bedescribed with reference to FIGS. 11A and 11B. FIG. 11A is a schematicplan view illustrating a planar arrangement of light sources, a lightguide plate, and photodetectors of an illuminating device according to aseventh embodiment. FIG. 11B is a schematic longitudinal cross-sectionalview taken along the line XIB2-XIB2 of FIG. 11A. Here, the sameconstituent elements as those of the illuminating device 100 accordingto the first embodiment are denoted by the same reference numerals.Thus, the description thereof will be omitted.

In this embodiment, one photodetector 731 is disposed to face an endface 120 b, and the other photodetector 732 is disposed to face a bottomsurface 122 of a light guide plate 120. Specifically, the photodetector731 is disposed to face an end portion of an end face 120 b toward anend face 120 c, and the photodetector 732 is disposed to face a bottomsurface portion that is adjacent to a central portion of the end face120 c.

In this way, by the two photodetectors 731 and 732, it is possible toreduce an effect on the control due to a variation of light that isemitted toward different directions from a light guide plate 120, and itis also possible to reduce an effect on the control due to a variationof the central portion and the end portion when viewed in a directionwhere the light sources are arranged.

Meanwhile, the photodetector 731 may be disposed to face an end face 120d. In contrast, the photodetector 731 may be disposed to face the bottomsurface portion that is adjacent to the end portion of the end face 120b, and the photodetector 732 may be disposed to face the central portionof the end face 120 c of the light guide plate 120. Further, thephotodetector that is disposed to face the bottom surface portion may bedisposed to face the light-emitting surface 121, not the bottom surface122.

Electronic Apparatus

Finally, an electronic apparatus mounted with the electro-optical deviceincluding the illuminating device will be described in detail. FIG. 12is a view illustrating the appearance of a notebook computer accordingto an embodiment of an electronic apparatus. This notebook computer 1000includes an operation unit 1001 and a display unit 1002, and anelectro-optical device 900 including an illuminating device 100 isdisposed in the display unit 1002. Here, the illuminating device 100 isused as a backlight of an electro-optical panel 800, and a displayscreen of the electro-optical panel 800 can be visibly recognized on thesurface of the display unit 1002.

Further, FIG. 13 is a view illustrating the appearance of a cellularphone according to another embodiment of the electronic apparatus. Thiscellular phone 2000 includes an operation unit 2001 and a display unit2002, and an electro-optical device 900 including an illuminating device100 is disposed in the display unit 2002. Here, the illuminating device100 is used as a backlight of an electro-optical panel 800, and adisplay screen of the electro-optical panel 800 can be visiblyrecognized on the surface of the display unit 2002.

The invention is not limited to the above-mentioned embodiments, but canbe appropriately modified without departing from the subject matter andspirit of the invention read in the claims and specification. Forexample, the electro-optical panel formed of the liquid crystal displaybody is used in the electro-optical device 900, but a differentelectro-optical display body capable of performing transmissive displaymay be used in the electro-optical device 900. Further, the illuminatingdevice 100 is used as the backlight of the electro-optical panel 800,but may be used as a frontlight thereof.

1. An illuminating device comprising: a plurality of light sources; a light guide plate that has plate surfaces on front and rear sides and a plurality of end faces formed around the plate surfaces, receives light emitted from the plurality of light sources through a light incident surface, and emits the light through a light-emitting surface, which is one of the plate surfaces; a plurality of photodetectors that are disposed to face the end faces or the plate surfaces of the light guide plate, and detects the light from the light guide plate; and a light source control unit that controls light emission of the plurality of light sources on the basis of the output of the plurality of photodetectors, wherein the plurality of photodetectors include at least two photodetectors including light receiving surfaces that face the end faces or the plate surfaces in different directions from each other.
 2. The illuminating device according to claim 1, wherein the light guide plate has a rectangular shape in plan view, and the plurality of photodetectors include at least two adjacent photodetectors that have light receiving surfaces that are disposed to face two of the end faces and the plate surfaces of the light guide plate that are adjacent to each other.
 3. The illuminating device according to claim 1, wherein the light source control unit collectively controls the plurality of light sources on the basis of representative values, which are derived from the detection values detected by the plurality of photodetectors.
 4. The illuminating device according to claim 1, wherein the light sources control chromaticity of emitted light, the photodetectors output detection values with which chromaticity of detected light can be derived, and the light source control unit collectively controls chromaticity of emitted light of the plurality of light sources on the basis of representative values of chromaticity that are derived from the detection values of the plurality of photodetectors.
 5. The illuminating device according to claim 1, wherein the light sources control luminance of emitted light, the photodetectors output detection values with which luminance of detected light can be derived, and the light source control unit collectively controls luminance of emitted light of the plurality of light sources on the basis of representative values of luminance that are derived from the detection values of the plurality of photodetectors.
 6. An electro-optical device comprising: the illuminating device according to claim 1; and an electro-electronic panel that is disposed on a light emitting side of the illuminating device and functions on the basis of illumination light of the illuminating device.
 7. An electronic apparatus comprising the electro-optical device according to claim
 6. 8. An illuminating device comprising: a plurality of light sources; a light guide plate that has plate surfaces on front and rear sides and a plurality of end faces formed around the plate surfaces, receives light emitted from the plurality of light sources through a light incident surface, and emits the light through a light-emitting surface, which is one of the plate surfaces; a plurality of photodetectors that are disposed to face the end faces of the light guide plate, and detects the light from the end faces of the light guide plate; and a light source control unit that controls light emission of the plurality of light sources on the basis of the output of the plurality of photodetectors, wherein the plurality of photodetectors include at least two photodetectors including light receiving surfaces that face the end faces or the plate surfaces in different directions from each other.
 9. An illuminating device comprising: a plurality of light sources; a light guide plate that has plate surfaces on front and rear sides and a plurality of end faces formed around the plate surfaces, receives light emitted from the plurality of light sources through a light incident surface, and emits the light through a light-emitting surface, which is one of the plate surfaces; a plurality of photodetectors that are disposed to face an outer circumferential portion of the plate surfaces of the light guide plate, and detects the light from the outer circumferential portion of the plate surfaces of the light guide plate; and a light source control unit that controls light emission of the plurality of light sources on the basis of the output of the plurality of photodetectors, wherein the plurality of photodetectors include at least two photodetectors including light receiving surfaces that face the end faces or the plate surfaces in different directions from each other. 